Minimization of defects in Nb-doped TiO2 photocatalysts by molten salt flux

Transition metal doping is a popular pathway to improve the photocatalytic performance of TiO2. However, most dopants are aliovalent (e.g., Nb5+, W6+, and Fe3+), where defects are inevitably introduced (e.g., oxygen or Ti3+ defects). To minimize defects and hence ensure better separation of photogenerated charges, this work incorporates an Nb dopant into TiO2 in a flux of molten salt. The molten salt flux not only induces recrystallization of TiO2 nanoparticles into nanowires but also allows a + 4 valence dopant in the TiO2 lattice to inhibit formation of Ti3+ or oxygen defects. This minimization of defects enhances the photocatalytic activity in the degradation of gaseous acetaldehyde. This enhancement is mainly attributed to the higher crystallinity of TiO2 and better separation of charge carriers induced by equivalent Nb-doping.